Hydraulic apparatus



Aug. 9, 1966 E. v. WARD HYDRAULIC APPARATUS Filed Jan. 4, 1965 Fla. 2.

INVEZMTOE gpwaxu V- WAR) United States Patent 3,265,008 HYDRAULIC APPARATUS Edward V. Ward, Cheltenham, England, assignor to Boulton Paul Aircraft Limited, Wolverhampton, England, a British company Filed Jan. 4, 1965, Ser. No. 423,014 Claims priority, application Great Britain, Jan. 6, 1964, 558/64 6 Claims. (Cl. 103162) This invention relates to hydraulic pumps or motors and more particularly although not exclusively to a motor for operation at low rotary speed and high torque.

In accordance with the present invention a pump or motor comprises a rotary cylinder barrel having a plurality of cylinders disposed parallel or nearly parallel to the rotation axis, a piston in each cylinder projecting from one end of the barrel, a drive shaft extending from the barrel, a block having a flat surface disposed adjacent to one end of the barrel, the flat surface being inclined or inclinable to the barrel rotation axis, a supply port and a return port opening into the flat surface, a slipper mounted by a ball joint at the outer end of each piston, a valve rotatably mounted on the block and having one surface engaging the fiat surface of the block, another surface, opposite to the said one surface, engaging the slippers, a-nd cylinder ports extending between the two surfaces of the valve, a hydraulic passage extending through each piston and slipper assembly to connect a cylinder with a cylinder port, and drive means interconnecting the barrel and valve to ensure their rotation at similar speeds, whereby each cylinder port is connected to the supply port during one part of a complete revolution of the cylinder barrel and is connected to the return port during another part of the complete revolution of the cylinder barrel so that liquid enters each cylinder from the supply port and is discharged from that cylinder through the return port.

The cylinders may extend completely through the barrel and within each cylinder a second piston is provided extending from the end of the barrel opposite to the said one end, a second block adjacent to the said opposite end of the cylinder barrel having a flat surface inclined to the block rotation axis, and second slipper means by which the second pistons engage the flat surface of the second block, the inclinations of the two flat surfaces being arranged to ensure opposite reciprocation of the two pistons in each cylinder during barrel rotation.

The drive means between the barrel and the valve may comprise a bevel gear drive.

The slippers mounted on the first pistons may each include a landed surface to contact the slipper surface of the valve, each landed surface comprising a circular land enclosing a recess whose area is slightly smaller than the cross section of the associated piston, whereby hydraulic forces on each first piston and slipper assembly are almost balanced leaving a slight hydraulic force only to urge each slipper onto the slipper surface.

One embodiment of the invention, intended for use as a slow speed high torque hydraulic motor, will now be described with reference to the accompanying drawings in which,

FIGURE 1 is .a cross section through the motor, and

FIGURE 2 is a cross section through the valve and block disposed at one end of the motor to illustrate details of the co-operating surfaces.

Referring initially to FIGURE 1 a rotary cylinder barrel 1 is rotatably mounted within a casing 2 having se cured to either end blocks 3 and 4. A pair of drive shafts respectively 5 and 6 extend one from each end of the cylinder barrel 1 and are located by taper roller bearings respectively 7 and 8 in the blocks 3 and 4. A hole 9 may 3,265,008 Patented August 9, 1966 be bored centrally through the drive shafts and the barrel to reduce the total mass of the motor.

Within the barrel 1 a plurality of cylinder bores 11 are formed which extend from end-to-end of the barrel in a direction substantially parallel with the rotation axis. Preferably there are an odd number of cylinders which are spaced evenly around the rotation axis. Within each cylinder a pair of pistons 12, 13 are slidably located, a compression spring 14 acting between the pistons to urge them outwardly from either end of the cylinder barrel. Each piston 13 is provided at its outer end with a ball joint 15 to carry a slipper 16. Each of the slippers 16 engages on a flat surface 17 of the block 3, the flat surface being iinciined to the rotation axis of the block 1. A small passage 18 extends through each piston 13 to the associated ball joint and slipper 15 .and 16 for lubrication of the ball joint and of the slipper in its contact with the surface 17 The block 4 includes adjacent to the cylinder barrel an inclined surface 19 around which is formed a circular rim 21. The surface 19 is inclined to the rotation axis of the barrel 1 oppositely to the inclination of the surface 17. The surface 19 is flat and on it is mounted a rotary Valve plate 22 which has a flat valve surface 23 which co-operates with the surface 19. Valve member 22 has a further flat surface 24 referred to as the slipper surface disposed on the opposite side to the valve surface 23. Around the periphery of the valve plate 22 a set of bevel gear teeth 25 are formed which mesh with a corresponding set of bevel gear teeth 26 formed around the periphery of the adjacent end of the cylinder block 1. These bevel gear teeth are arranged to ensure that both the block 1 and the valve plate 22 rotate in exact synchronism about their respective rotation axes which are of course inclined to one another.

The outer end of each piston 12 carries a ball joint 27 which in turn carries a slipper 28 engaging the slipper surface 24. Through the piston 12 and the ball joint 27 a passage 29 of substantial cross section extends. The surface of the slipper 28 which contacts the slipper surface 24 of the valve plate is formed as a circular land 31 which encloses a circular recess 32. The circular recess 32 is of a diameter slightly less than the diameter of the piston 12 so that the action of hydraulic pressure in the cylinder 11 will urge slipper 28 against the slipper surface with a comparatively small force even though the hydraulic pressure is high. This results from the counter balancing action of hydraulic pressure acting in the recess 32. Within the valve plate, for each piston 12, there is provided a port 33 which extends between the surfaces 23 and 24 of the valve plate. These ports are equally spaced around the valve plate and due to the engagement of the bevel gear teeth 25 and 26 it will be found that during cylinder barrel rotation each slipper recess 32 continually covers its associated port 33. Due to the inclination of the rotation axes of the barrel 1 and the valve plate 22 each slipper 28 will oscillate slightly on the valve surface 23 during rotation, but it will always cover and make hydraulic connection with the port 33.

Within the side walls of the block 4 a pair of hydraulic connections 34 and 35 are formed. From the connection 34 a passage 36 leads to a kidney-shaped port 37 in the block surface 19. Similarly from the connections 35 a passage 38 leads to a kidney-shaped port 39 also formed in the surface 19. During rotation of the barrel 1 and the valve plate 22 each port 33 in the valve plate will alternately connect with the kidney ports 37 and 39. These ports 37 and 39 are so arranged that as each port 33 passes from one to the other the pistons 12 and 13 in the associated cylinder are either at their innermost position or at their outermost position. In FIGURE 1 the ports 37, 39, the passages 36,

37 and the connections 34, 35 appear in the section through the block 4 although they are not, in fact, located in this section. They have been shown in this position solely for ease of understanding. Their correct position is as shown in FIGURE 2.

For operation as a motor a high pressure hydraulic source is connected to one of the connections 34 and 35 and the other of these connections is connected to a return passage leading to a lower pressure zone. Assume for example that high pressure is connected to the connection 34. Such high pressure will then pass to the kidney port 37, through all cylinder ports 33 in connection with the kidney port 37 and through the associated passages 29 to the cylinders 11. The action of pressure within these cylinders 11 will urge the pistons 12 and 13 outwardly and the reaction against the inclined surface 17 at one end and against the inclined surface 19 at the other end produces forces of which one component acts tangentially through the slippers and the pistons on the cylinder barrel to cause it to rotate. Another substantial component of the forces exerted by the slippers 16 and 28 lies in a direction parallel to the rotation axis of the barrel but this component is resisted by tension in the casing 2 which holds the blocks 3 and 4 in their relative positions. The axial forces in the described embodiment are exactly equal for each pair of pistons 12 and 13 in each cylinder with the result that there is substantially no end load hydraulically applied to the cylinder barrel 1. The taper roller bearings 7 and 8 hold the barrel in position for rotation against the vary substantial radial forces which are reacted from the slippers onto the cylinder barrel. The taper roller bearings also serve the further function of holding the cylinder barrel in its correct axial position for engagement of the bevel gear teeth 25 and 26.

The total area of each kidney port 37 or 39 is so arranged that it is slightly less than the total cross-sectional area of the minimum number of pistons 12 that are in hydraulic connection with it at any one time.

In this way the mechanical force exerted by a piston 12 on a slipper 28 is transmitted almost completely by hydraulic force to the inclined surface 19 with a result that the valve plate 22 has little frictional resistance to rotation.

Whilst in the described embodiment the drive means interconnecting the barrel 1 to the valve plate 22 has been shown as a pair of bevel gears it will be appreciated that many other drive means may be provided. For example, a small recess may be provided in the slipper surface of the valve plate for each slipper 28, these recesses being of .sufiicient size to permit the slight relatively oscillation between the slipper and the valve plate. Engagement of the slippers with the edges of their co-operating recesses then rotates the valve plate. Again alternatively the valve plate may be mounted on a splined part spherical projection of the drive shaft 16 which extends from the barrel 1, the splines interconnecting the valve plate with the shaft to rotate with the shaft but to permit the valve plate to remain seated on the blocksurface 19. The illustrated embodiment offers the following advantages over more conventional low speed high torque motors:

(a) The drive shaft may extend from both ends of the cylinder barrel to transmit driving torque.

(b) The valve takes up very little room so that the overall dimensions of the motor are kept substantially to the minimum.

(c) The position of the valve permits a hole to extend completely through the cylinder barrel and drive shaft reducing total mass of the motor.

(d) The valve produces effectively no end thrust on the cylinder barrel other than for thrust exerted by the pistons.

(e) The cylinder barrel may operate completely balanced axially having regard to the operating hydraulic forces giving rise to little or no end thrust on the cylinder barrel bearings.

Whilst the describfid embodiment of the invention shows a motor having two oppositely extending pistons in each cylinder it will be appreciated that within the broad scope of the present invention the cylinder barrel may be single ended i.e. the pistons 13 and the inclined surface 17 could be omitted from the described construction, the cylinders being closed at their ends remote from the pistons 12. In such a case it would be necessary to provide end thrust bearings for the cylinder barrel to resist the hydraulic axial thrust that would be exerted on the barrel.

Further whilst the described embodiment shows a construction where the inclined flat surfaces at the ends of the block are fixed in inclination it is equally within the scope of the specification that either one or both of such surfaces should be adjustable as to its inclination relative to the drive shaft axis. For example, in the described embodiment the fiat surface 17 could be formed on a swash plate member mounted for tilting movement on trunnions whose tilt axis is disposed perpendicularly to the rotation axis of the barrel 1. Assuming that such a swash plate were adjustable to incline its surface 17 from the position shown in FIGURE 1 to a position which is parallel to the inclined surface 19 it would be possible to vary the displacement of the motor from a maximum value down to zero, the zero value occurring when the two surfaces 17 and 19 are parallel.

This arrangement would still possess the advantages (a), (b), (c), (d), (e) set out above.

I claim as my invention:

1. A pump or motor comprising a rotary cylinder barrel having a plurality of cylinders disposed parallel or nearly parallel to the rotation axis, a piston in each cylinder projecting from one end of the barrel, a drive shaft extending from the barrel, a block having a fiat surface disposed adjacent to one end of the barrel, the flat surface being inclined or inclinable to the barrel rotation axis, a supply port and a return port opening into the flat surface, a slipper mounted by a ball joint at the outer end of each piston, a valve rotatably mounted on the block and having one surface engaging the flat surface of the block, another surface, opposite to the said one surface, engaging the slippers, and cylinder ports extending between the two surfaces of the valve, a hydraulic passage extending through each piston and slipper assembly to connect a cylinder with a cylinder port, and drive means interconnecting the barrel and valve to ensure their rotation at similar speeds, whereby each cylinder port is connected to the supply port during one part of a complete revolution of the cylinder barrel and is connected to the return port during another part of the complete revolution of the cylinder barrel so that liquid enters each cylinder from the supply port and is discharged from that cylinder through the return port.

2. A pump or motor as claimed in claim 1 wherein the cylinders extend completely through the barrel, and including a second piston in each cylinder extending from the opposite end of the barrel to the first mentioned piston, a second block adjacent the said opposite end of the cylinder barrel having a flat surface inclined to the block rotation axis, and slipper means by which the second pistons engage the flat surface of the second block, the inclination of the two flat surfaces being arranged to ensure opposite reciprocation of the two pistons in each cylinder during barrel rotation.

3. A pump or motor as claimed in claim 1 wherein the drive means comprises a bevel gear drive between the barrel and the valve.

4. A pump or motor as claimed in claim 1 wherein the slippers attached to the first pistons each include a landed surface which contacts the said other surface of the valve, each landed surface comprising a circular land enclosing a recess whose area is slightly smaller than the cross section of the associated piston whereby hydraulic forces on each piston and slipper are almost balanced leaving a slight hydraulic force only to urge the slipper onto the said other surface.

5 A pump or motor as claimed in claim 1 wherein in the valve and through a central hole in the block which the total area of the supply or return port under pressure carries the valve. is slightly less than the total area of the minimum number n of cylinders that may be in connection with it through Relerences Cted by the Exammel' the cylinder ports at any one time, such that hydraulic 5 UNITED STATES PATENTS forces acting on the valve in a direction parallel to its 2,821,932 2/1958 Lucien 1O3 173 rotation axis are almost balanced leaving a slight hy- 3,056,358 10/1962 Pedersen et a1 draulic force only by Which the pistons may act through 3,200,762 8/1965 Thoma 1 3 1 2 the slippers to hold the valve on the flat surface.

6. A pump or motor as claimed in claim 1 wherein the 10 MARK NEWMAN Pmnmy Examine"- drive shaft extends from the barrel through a central hole R. M. VARGO, Assistant Examiner. 

1. A PUMP OR MOTOR COMPRISING A ROTARY CYLINDER BARREL HAVING A PLURALITY OF CYLINDERS DISPOSED PARALLEL OR NEARLY PARALLEL TO THE ROTATION AXIS, A PISTON IN EACH CYLINDER PROJECTING FROM ONE END OF THE BARREL, A DRIVE SHAFT EXTENDING FROM THE BARREL, A BLOCK HAVING A FLAT SURFACE DISPOSED ADJACENT TO ONE END OF THE BARREL, THE FLAT SURFACE BEING INCLINED OR INCLINABLE TO THE BARREL ROTATION AXIS, A SUPPLY PORT AND A RETURN PORT OPENING INTO THE FLAT SURFACE, A SLIPPER MOUNTED BY A BALL JOINT AT THE OUTER END OF EACH PISTON, A VALVE ROTATABLY MOUNTED ON THE BLOCK AND HAVING ONE SURFACE ENGAGING THE FLAT SURFACE OF THE BLOCK, ANOTHER SURFACE, OPPOSITE TO THE SAID ONE SURFACE, ENGAGING THE SLIPPERS, AND CYLINDER PORTS EXTENDING BETWEEN THE TWO SURFACES OF THE VALVE, A HYDRAULIC PASSAGE EXTENDING THROUGH EACH PISTON AND SLIPPER ASSEMBLY TO CONNECT A CYLINDER WITH A CYLINDER PORT, AND DRIVE MEANS INTERCONNECTING THE BARREL AND VALVE TO ENSURE THEIR ROTATION AT SIMILAR SPEEDS, WHEREBY EACH CYLINDER PORT IS CONNECTED TO THE SUPPLY PORT DURING ONE PART OF A COMPLETE REVOLUTION OF THE CYLINDER BARRL AND IS CONNECTED TO THE RETURN PORT DURING ANOTHER PART OF THE COMPLETE REVOLUTION OF THE CYLINDER BARREL SO THAT LIQUID ENTERS EACH CYLINDER FROM THE SUPPLY PORT AND IS DISCHARGED FROM THAT CYLINDER THROUGH THE RETURN PORT. 